1. Field of the Invention
The present invention relates to a projection display device that modulates light from a light source and projects the modulated light onto a projection plane.
2. Disclosure of Related Art
A projection display device (hereinafter, referred to as “projector”) modulates light from a light source by an imager, and projects the modulated light (hereinafter, referred to as “image light”) onto a projection plane.
Such a projector may be configured for contrast feeling enhancement to adjust the amount of light radiated to the imager, in accordance with brightness of an image to be projected onto the projection plane. For example, an aperture mechanism variable in size of an opening (hereinafter, referred to as “amount of opening”) is provided in the middle of a light path from the light source to the imager. Based on an input image signal, an average picture level (APL) is determined, and the amount of opening of the aperture mechanism is more reduced with the smaller APL.
However, when the amount of light from the light source is reduced by the aperture mechanism as described above, part of the light is blocked out by the aperture mechanism. Accordingly, the amount of the light radiated to the imager is likely to vary, and thus images projected onto the projection plane are prone to have color unevenness.
In the case of projecting moving images, the images are in motion and change quickly, and thus color unevenness in the images is inconspicuous. In particular, pictures in movies and TV programs are formed frequently in variety of colors and are further inconspicuous in color unevenness. Therefore, color unevenness is unlikely to become a problem with moving images.
Meanwhile, in the case of projecting still images, the images are motionless and change extremely slowly, and thus color unevenness in the images is conspicuous. In addition, still images of drawings as information materials for making a presentation or the like, are frequently prepared in a smaller number of colors, which makes color unevenness in the images further conspicuous.
Moreover, color unevenness is more conspicuous in brighter images.
Therefore, regardless of still images or moving images, a high contrast feeling can be obtained if the amount of light is adjusted in the same manner between dark to bright images. However, color unevenness may be significantly conspicuous in bright still images.
On the other hand, color unevenness can be made inconspicuous even in still images if the amount of light is adjusted only for dark images. In such an arrangement, however, contrast feeling is unnecessarily deteriorated in moving images.